II. Field of the Invention
The present invention relates to sterilization and disinfection systems that utilize gas or vapor phase sterilants or disinfectants and, more particularly, to low-temperature, hydrogen peroxide vapor sterilization systems.
III. Related Art
Low temperature application of hydrogen peroxide vapor is highly effective when sterilizing objects having relatively open and accessible surfaces such that the hydrogen peroxide vapor can easily surround and contact all surfaces of the object and sterilize these surfaces. To date, low temperature application of hydrogen peroxide vapor has proven to be more difficult when sterilizing objects having diffusion limited interiors and particularly long, narrow lumens. This is because hydrogen peroxide vapor degrades to water and oxygen over time when coming in contact with many materials used to form the surface of such lumens. Thus, the hydrogen peroxide vapor degrades as it diffuses into the interior of the lumen due to the large surface to cross-section ratio of the lumen. Water droplets collecting in the interior of the lumen can block the passage of hydrogen peroxide vapor into the lumen. This degradation limits the diametric size and lengths of lumens that can be sterilized with current vapor-phase hydrogen peroxide systems. There is a need for improved systems and methods to enhance the penetration of vapor sterilants down long narrow objects such as the lumens of tubular devices.
A variety of methods have been employed to sterilize objects having long, narrow lumens, but each of these methods has its shortcomings. Liquid sterilants have been employed in systems commonly referred to as endoscope reprocessors. These systems can combine some of the cleaning and disinfecting steps into a single device. However, the final step is a water rinse which reduces the effectiveness of such systems. Reprocessors are able to provide high level disinfection, but are incapable of sterilizing such objects
Dry boosters and wet boosters have been coupled to lumen devices for sterilization purposes. A dry booster is an object with an internal volume that is typically coupled to one end of the lumen of a device before the device is placed in a vacuum chamber. When the lumen and booster are at a vacuum, the sterilant vapor then added to the vacuum chamber passes through the lumen to fill in the void space of the booster. A wet booster is similar to a dry booster in that it is attached to a lumen device to be sterilized before the device is placed in the vacuum chamber. In the case of a wet booster, liquid sterilant is contained in the booster that vaporizes as the vacuum chamber is evacuated. This draws sterilant vapor from the wet booster through the lumen to sterilize the device. Dry and wet boosters are time consuming and clumsy to use. The use of such devices also introduces mated surfaces between the booster and the lumen device which are difficult to sterilize.
Special sterilization trays have also been described in prior art. These trays have a sealable barrier defining two volumes. The tray is also equipped so that a pressure differential can be created between the two volumes. Generally, when these trays are employed the lumen device is placed across the sealable barrier with the two ends of the lumen on opposite sides of the barrier. When sterilant is added to the higher pressure side of the barrier, the pressure differential causes the sterilant to flow through the lumen device toward the lower pressure side of the barrier to sterilize the lumen. Such sterilization trays are also cumbersome to use and introduce mated surfaces between the barrier and tubular wall defining the lumen of the device which are difficult to sterilize.
Various methods to concentrate hydrogen peroxide by removing water have also been described in prior art. Increasing the vapor concentration of hydrogen peroxide outside a lumen provides a greater potential for the hydrogen peroxide to diffuse into a lumen before degrading to low levels. It also reduces the concentration of water vapor, which may prevent hydrogen peroxide from reaching surfaces. The concentration of aqueous hydrogen peroxide that can be shipped by air, however, is limited to about 59% and requires that only small volumes are present in each container. Several methods have been described in prior art to increase the vapor concentration above that of 59% hydrogen peroxide. These are generally methods to remove some of the water vapor with a vacuum pump while retaining much of the hydrogen peroxide. These methods have improved lumen penetration, but at the cost of greater material degradation of the items that are sterilized due to the exposure to highly concentrated hydrogen peroxide vapor.
These prior art methods described above have shortcomings solved by the present invention. The present invention allows full sterilization of the load even when the load includes devices having long, narrow lumens. In addition, the present invention does not employ special devices that must be coupled to the lumen device or special trays of the type described above. Finally, the present invention does not increase the overall concentration of hydrogen peroxide, but rather redistributes the concentration of hydrogen peroxide to the inside of lumens thus maintaining overall material compatibility with the sterilization process.
An object of the present invention is to provide a sterilization system with enhanced sterilant penetration into lumen devices.
Another object of the invention is to provide a sterilization system with a sterilization area variable in size.
Still another object of the invention is to provide a sterilization system having a sterilization area with a movable boundary.
A further object of the invention is to provide a sterilization system with a sterilization area, the size of which can be compressed or expanded in a controlled fashion.